Testers for evaluating robustness of electronic devices against electrostatic discharge signals are of great importance in order to be able to establish which operating and environmental conditions can withstand the electronic device.
Electrostatic discharge (ESD) signals can occur while handling the device in industrial or commercial environments. ESD failures can be difficult to detect because ESD events are unpredictable and difficult to reproduce in laboratory tests. A good ESD strategy at device level and testers capable of reliable ESD test results are thus of utmost importance for commercializing electronic device in high volume with very limited ESD failure rates.
An ESD tester typically measures several electrical characteristics of each externally accessible terminal of the device before and after delivering the ESD signal to the terminal.
However, in order to measure these electrical characteristic of each externally accessible terminal of the device, a measurement device (for example an I-V tracer or any other measurement device) is typically electrically connected to each device terminal via a respective measurement terminal of the measurement device. Electrical switches may be used which electrically decouple the device terminals from the measurement terminals when the ESD signal is delivered to a terminal of the device and electrically couple the device terminals to the measurement terminals when the device terminal is tested after the ESD signal has been delivered. However, electrical isolation provided by the electrical switches may be not sufficient to electrically isolate the measurement device from the ESD signal, thereby a risk exists to damage the measurement device during delivering the ESD signal. Further, electrical switches have parasitic capacitances which charge while delivering the ESD signal, i.e. when the electrical switches are switched off, and discharge while testing the device terminal, i.e. when the electrical switches are switched on, thereby changing the level of ESD stress delivered to the device. As a consequence the resulting ESD test from known ESD testers is not reliable.